1. Field of the Invention
The present invention relates to exchange coupled films that employ antiferromagnetic layer and ferromagnetic layer and a magnetoresistance effect element that are used for magnetic field detecting sensors, reproducing magnetic heads, and the like.
2. Description of the Related Art
For high density magnetic recording, magnetic heads that employ a magnetoresistance effect are being studied. As a material of magnetoresistance devices, an alloy thin film made of 80 atomic % of Ni and 20 atomic % of Fe (this alloy is generally referred to as permalloy) has been used. In recent years, as a substitute of this material, a multilayer film and a spin valve film such as Co/Cu with a giant magnetoresistance effect are becoming popular.
However, magnetoresistance films made of such materials have magnetic domains and thereby are particularly susceptible to Barkhausen noise. Various methods have been studied so that such magnetoresistance films have a single magnetic domain. N represents the metal which is preferably used with an exchange coupling of a magnetoresistance film, which is made of a ferromagnetic material and an antiferromagnetic material, to a predetermined direction. For example, Hempstead et al. in U.S. Pat. No. 4,103,315 for "ANTIFERROMAGNETIC-FERROMAGNETIC EXCHANGE BIAS FILMS", Abstract teach "In thin film magnetic transducers, e.g., inductive or magnetoresistance recording heads, at least a pair of layers of a ferromagnetic material and an antiferromagnetic material are deposited upon one another and exchange coupled to retain a unidirectional bias in the plane of the ferromagnetic material." In this related art reference, a FeMn alloy is used for an antiferromagnetic material.
However, the FeMn alloy tends to become corroded especially by acid. Thus, the exchange coupling force of the FeMn alloy to the magnetoresistance film degrades over time.
In addition, Hempstead et al. supra disclose .gamma.-Mn alloys (such as MnPt alloy and MnRh alloy) and oxides (such as NiO) as antiferromagnetic materials. However, the exchange coupling force of the .gamma.-Mn alloys is not satisfactory. On the other hand, insulating oxides such as NiO, which have high electric resistances, cannot be directly provided with electrodes in this area, thereby complicating the device construction.
Another related art reference disclosed as U.S. Pat. No. 5,014,147 teaches "An improved thin film magnetoresistance (MR) sensor uses an alloy comprising Fe.sub.(1-x) Mn.sub.x, where x is within range of 0.3 to 0.4, as an antiferromagnetic layer to provide longitudinal exchange bias in the ferromagnetic MR layer."
Thus, in this related art reference, the FeMn Alloy tends to be corroded and the exchange coupling force of the antiferromagnetic material with the magnetoresistance film degrades over time.